A conventional internal combustion engine uses either a cam and push rod system or a direct acting overhead cam operating on a rocker-arm to actuate the engine poppet valves. The camshaft typically runs the length of the engine and is driven by a gear train off of the crankshaft. The engine valve timing events are fixed with respect to the crankshaft position and the lift rate of the valve is proportional to engine speed. These restrictions upon the engine valves induce compromises in engine performance regarding fuel consumption, emissions, torque, and idle quality. To minimize these compromises, numerous methods have been introduced to vary the phasing of the intake and exhaust valve cams relative to crankshaft position. The variable valve actuation mechanisms are inherently costly and complex.
The diesel engine camshaft with direct fuel injection typically has a cam to drive the injector plunger. The fuel injector cam .[.lob.]. .Iadd.lobe .Iaddend.is especially prone to durability problems with high pressure fuel injection systems. In another type system, as taught in U.S Pat. No. 4,009,695 which issued on Mar. 1, 1977 to Louis A. Ule, the valves are operated by two separate valve assemblies which are moved in response to a mechanical apparatus which is controlled by engine speed.
The subject invention combines direct high pressure fuel injection with intake and exhaust valve actuation in a single hydraulically powered device. The subject invention replaces the camshaft and conventional valve train components thereby reducing the engine part count and maintenance. The subject invention has the ability to electronically adjust valve and fuel injection timing which provides a freedom to optimize engine performance at any engine load or speed. The subject invention allows a modular approach to engine design which would be difficult to accomplish with a mechanical valve train system.